Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$244.66	6.861%	$261.4461	$261.45	$261.45	$261.40
Purchase #2	$195.76	10.109%	$215.5494	$215.55	$215.55	$215.50
Purchase #3	$66.38	11.169%	$73.794	$73.79	$73.80	$73.80
Purchase #4	$55.81	10.814%	$61.8453	$61.85	$61.85	$61.80
Purchase #5	$66.46	10.517%	$73.4496	$73.45	$73.45	$73.40
Purchase #6	$246.66	11.500%	$275.0259	$275.03	$275.05	$275.00
Purchase #7	$164.56	11.347%	$183.2326	$183.23	$183.25	$183.20
7 purchase totals =	$1,040.29		$1,144.3429	$1,144.35	$1,144.40	$1,144.10